If I figured it right I have a cylinder 90 gallon fresh water tank ( it measures 20" diameter and 65" in height., and a rectangle 120 gallon black tank that measures 15' high 28 wide and 64 inches long. Both tanks can be filled or drained from either side.

Here in AZ and other states the dumping of grey water is against the law,but the dumping of wash water (shower) is not a system with the kitchen sink tied into the tank where food particles are in the water is classified as sewage in most states just passing it on

But my neighbors dog can poop on my lawn every morning and evening. I don't buy into that silliness and hence have a hidden (routed next to the air tank between my rear duals) drain exit. 95% of the time, we have a sewer connection and it isn't an issue, but when parked on the side of the road or near parking lot drain, and showering, well...yeah.

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